Securities (Amortized Cost and Fair Value of Debt Securities Available for Sale) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale [Line Items]
Securities available for sale, amortized cost	$ 6,085,309	$ 6,310,214
Securities Available for Sale, Gross unrealized gains	68	2,315
Securities Available for Sale, Gross unrealized losses	897,221	756,488
Securities Available for Sale, Fair value	5,188,156	5,556,041
U.S. Treasury And Government Agency Securities [Member]
Debt Securities, Available-for-Sale [Line Items]
Securities available for sale, amortized cost	118,208	113,211
Securities Available for Sale, Gross unrealized losses	4,018	2,346
Securities Available for Sale, Fair value	114,190	110,865
Municipal Obligations [Member]
Debt Securities, Available-for-Sale [Line Items]
Securities available for sale, amortized cost	204,445	207,014
Securities Available for Sale, Gross unrealized gains	44	59
Securities Available for Sale, Gross unrealized losses	11,378	3,981
Securities Available for Sale, Fair value	193,111	203,092
Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-Sale [Line Items]
Securities available for sale, amortized cost	2,424,225	2,655,381
Securities Available for Sale, Gross unrealized gains	24	224
Securities Available for Sale, Gross unrealized losses	463,682	398,619
Securities Available for Sale, Fair value	1,960,567	2,256,986
Commercial Mortgage-Backed Securities [Member]
Debt Securities, Available-for-Sale [Line Items]
Securities available for sale, amortized cost	3,250,230	3,234,278
Securities Available for Sale, Gross unrealized gains		2,032
Securities Available for Sale, Gross unrealized losses	408,879	342,880
Securities Available for Sale, Fair value	2,841,351	2,893,430
Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-Sale [Line Items]
Securities available for sale, amortized cost	64,701	76,830
Securities Available for Sale, Gross unrealized losses	5,871	6,242
Securities Available for Sale, Fair value	58,830	70,588
Corporate Debt Securities [Member]
Debt Securities, Available-for-Sale [Line Items]
Securities available for sale, amortized cost	23,500	23,500
Securities Available for Sale, Gross unrealized losses	3,393	2,420
Securities Available for Sale, Fair value	$ 20,107	$ 21,080

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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